A lunisolar calendar is a type of calendar that combines both lunar and solar cycles to determine the dates of months and years.

In a lunar calendar, the months are based on the cycles of the Moon, which takes about 29.5 days to complete a full cycle and 354.37 days to complete a lunar year. This means that a lunar month is about 29 or 30 days long. However, since the Earth’s orbit around the Sun is not synchronized with the Moon’s orbit, a lunar calendar doesn’t align with the solar year, which is about 365.24 days long. This is approximately 11 days shorter than the solar year, which is based on the Earth’s orbit around the Sun.

To solve this problem, a lunisolar calendar incorporates both lunar months and solar years by adding extra months or days to certain years so that the cycles match. This keeps the calendar in sync with both the phases of the Moon and the seasonal changes caused by the Earth’s orbit around the Sun. Some have claimed in modern times that the Quran is based on this kind of lunisolar calendar, but this goes against the verses of the Quran and logic. This article aims to address the points that are commonly brought up in support of the lunisolar calendar.

Number of months according to Quran

The Quran informs us that the count of months according to God is twelve, which has been God’s law since He created the heavens and earth. If the calendar is based on a lunisolar, then there needs to be an additional month some years, making the number of months 13.

[9:36] The count of months, as far as GOD is concerned, is twelve.* This has been GOD’s law, since the day He created the heavens and the earth. Four of them are sacred. This is the perfect religion; you shall not wrong your souls (by fighting) during the Sacred Months. However, you may declare all-out war against the idol worshipers (even during the Sacred Months), when they declare all-out war against you, and know that GOD is on the side of the righteous.

 إِنَّ عِدَّةَ ٱلشُّهُورِ عِندَ ٱللَّهِ ٱثْنَا عَشَرَ شَهْرًا فِى كِتَـٰبِ ٱللَّهِ يَوْمَ خَلَقَ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضَ مِنْهَآ أَرْبَعَةٌ حُرُمٌ ذَٰلِكَ ٱلدِّينُ ٱلْقَيِّمُ فَلَا تَظْلِمُوا۟ فِيهِنَّ أَنفُسَكُمْ وَقَـٰتِلُوا۟ ٱلْمُشْرِكِينَ كَآفَّةً كَمَا يُقَـٰتِلُونَكُمْ كَآفَّةً وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ مَعَ ٱلْمُتَّقِينَ

Postponing Sacred Months is a sign of disbelief

If the additional month is added, then this would postpone the Sacred Months according to the Quran, and this would be a sign of excessive disbelief.

[9:37] Altering the Sacred Months is a sign of excessive disbelief; it augments the straying of those who have disbelieved. They alternate the Sacred Months and the regular months, while preserving the number of months consecrated by GOD. They thus violate what GOD has consecrated. Their evil works are adorned in their eyes. GOD does not guide the disbelieving people.

 إِنَّمَا ٱلنَّسِىٓءُ زِيَادَةٌ فِى ٱلْكُفْرِ يُضَلُّ بِهِ ٱلَّذِينَ كَفَرُوا۟ يُحِلُّونَهُۥ عَامًا وَيُحَرِّمُونَهُۥ عَامًا لِّيُوَاطِـُٔوا۟ عِدَّةَ مَا حَرَّمَ ٱللَّهُ فَيُحِلُّوا۟ مَا حَرَّمَ ٱللَّهُ زُيِّنَ لَهُمْ سُوٓءُ أَعْمَـٰلِهِمْ وَٱللَّهُ لَا يَهْدِى ٱلْقَوْمَ ٱلْكَـٰفِرِينَ

1innamāإِنَّمَاIndeed, that
2l-nasīuٱلنَّسِىٓءُthe postponing / altering (the Sacred Months)
3ziyādatunزِيَادَةٌincreases / exceeds / augments
5l-kuf’riٱلْكُفْرِthe disbelief,
6yuḍalluيُضَلُّit sends astray
7bihiبِهِby it
8alladhīnaٱلَّذِينَthose who
9kafarūكَفَرُوا۟[they] disbelieved.
10yuḥillūnahuيُحِلُّونَهُۥThey make it lawful / permit it
11ʿāmanعَامًاa [lunar] year
12wayuḥarrimūnahuوَيُحَرِّمُونَهُۥand they make it unlawful / prohibit it
13ʿāmanعَامًا(another) [lunar] year.
14liyuwāṭiūلِّيُوَاطِـُٔوا۟That they may adjust / make equal
15ʿiddataعِدَّةَ(the) number (of months)
17ḥarramaحَرَّمَ[He] made unlawful / Sacred
19fayuḥillūفَيُحِلُّوا۟then they make lawful / permit / violate
21ḥarramaحَرَّمَ[He] made unlawful / Sacred
23zuyyinaزُيِّنَIt was adorned
24lahumلَهُمْfor them
25sūuسُوٓءُ(the) evil (of)
26aʿmālihimأَعْمَـٰلِهِمْtheir deeds.
27wal-lahuوَٱللَّهُAnd God
29yahdīيَهْدِىHe guides
30l-qawmaٱلْقَوْمَthe people –
31l-kāfirīnaٱلْكَـٰفِرِينَthe disbelievers.

Sana & ʿām

The Quran uses two different words for year: “sanah” ( سنة ) and “ʿām” ( عام ). This shows that there are two different systems for determining the year according to the Quran. The difference between these two terms is that “sanah” ( سنة ) is in reference to the solar year, while “ʿām” ( عام ) is in reference to the lunar year.

This is best depicted in the following verse regarding the length of time the sleepers of the cave spent in the cave, stating that they stayed in the cave for 300 solar years; increased by nine.

[18:25] They stayed in their cave three hundred years, increased by nine.

(٢٥) وَلَبِثُوا۟ فِى كَهْفِهِمْ ثَلَـٰثَ مِا۟ئَةٍ سِنِينَ وَٱزْدَادُوا۟ تِسْعًا

1walabithūوَلَبِثُوا۟And they remained
3kahfihimكَهْفِهِمْtheir cave
4thalāthaثَلَـٰثَ(for) three
7wa-iz’dādūوَٱزْدَادُوا۟and they increased (by)

It just happens that 300 solar years is equivalent to 309 lunar years. This gives us two systems for calculating the time period in both solar and lunar. We see a similar structure regarding the age of Noah.

[29:14] We sent Noah to his people, and he stayed with them one thousand years (solar), less fifty (lunar). Subsequently, they incurred the flood because of their transgressions.

(١٤) وَلَقَدْ أَرْسَلْنَا نُوحًا إِلَىٰ قَوْمِهِۦ فَلَبِثَ فِيهِمْ أَلْفَ سَنَةٍ إِلَّا خَمْسِينَ عَامًا فَأَخَذَهُمُ ٱلطُّوفَانُ وَهُمْ ظَـٰلِمُونَ

1walaqadوَلَقَدْAnd verily,
2arsalnāأَرْسَلْنَاwe sent
5qawmihiقَوْمِهِۦhis people,
6falabithaفَلَبِثَand he remained
7fīhimفِيهِمْamong them
8alfaأَلْفَa thousand
10illāإِلَّاless / except
12ʿāmanعَامًا[lunar] year(s),

Additionally, since the religious rites mentioned in the Quran, e.g., fasting and Hajj, are determined by the lunar calendar, we see that these are used in conjunction with the term “ʿām” ( عام ) and never “sanah” ( سنة ). This is can be observed in verse 9:37 above as well as 9:28.

1ʿāminعَامٍ[lunar] year(s),2:259:20
2ʿāminعَامٍ[lunar] year(s).2:259:36
3ʿāmihimعَامِهِمْtheir [lunar] year9:28:12*
4ʿāmanعَامًاa [lunar] year9:37:11*
5ʿāmanعَامًا(another) [lunar] year.9:37:13*
6ʿāminعَامٍ[lunar] year9:126:7
7ʿāmunعَامٌa [lunar] year12:49:6
8ʿāmanعَامًا[lunar] year(s),29:14:12
9ʿāmayniعَامَيْنِtwo [lunar] years31:14:11
Every occurrence of ‘am in Quran
3bil-sinīnaبِٱلسِّنِينَwith [the] years (of famine)7:130:5
4l-sinīnaٱلسِّنِينَthe years10:5:12
7l-sinīnaٱلسِّنِينَthe years,17:12:18
10sinīnaسِنِينَ(some) years20:40:26
14sinīnaسِنِينَ(for) years.26:205:4
Every occurance of sana in Quran

Hajj and the Sacred Months

We know that Hajj and the Sacred Months are determined by the moon’s phases. If a lunar month is added or additional days are to be added to a lunar year to align the lunar and solar calendars, then these dates would defeat the ability to be able to reliably

[2:189] They ask you about the phases of the moon! Say, “They provide a timing device for the people, and determine the time of Hajj.” It is not righteous to beat around the bush; righteousness is attained by upholding the commandments and by being straightforward. You shall observe GOD, that you may succeed.

 يَسْـَٔلُونَكَ عَنِ ٱلْأَهِلَّةِ قُلْ هِىَ مَوَٰقِيتُ لِلنَّاسِ وَٱلْحَجِّ وَلَيْسَ ٱلْبِرُّ بِأَن تَأْتُوا۟ ٱلْبُيُوتَ مِن ظُهُورِهَا وَلَـٰكِنَّ ٱلْبِرَّ مَنِ ٱتَّقَىٰ وَأْتُوا۟ ٱلْبُيُوتَ مِنْ أَبْوَٰبِهَا وَٱتَّقُوا۟ ٱللَّهَ لَعَلَّكُمْ تُفْلِحُونَ


Another claim for the lunisolar calendar is pointed toward the etymology of the names of months in the Islamic calendar. The only month mentioned by name in the Quran is Ramadan. The the root ( ر م ض ) of the word Ramadan ( رَمَضَانَ ) means scorching heat, and some extract this to mean that Ramadan must fall during the time when it is hot, and this would go counter to a lunar calendar that shifts by ~11 days each year. The problem with this understanding is that when dealing with pronouns, it does not always correspond with the root meaning.

This is because pronouns used in the form of the name are meant in reference to themselves rather and may have no bearing to the origin of the name. For instance, the root of the name Jesus ( عِيسَى ) in Arabic comes from the root ( ع ي س ), which has the meaning of “a camel of a white colour mixed with somewhat of [the red hue termed] or [dingy white;] white with a slight darkness (Mṣb:) or inclining to yellow: [i. e., yellowish white:].” But the name Jesus and the etmology of the Arabic root are completely unrelated, and it wouldn’t make sense to look at the triliteral root to understand the meaning of his name.

Even in the Gregorian, if we look at the names of the twelve months, each name has its own etymology. Still, if your spouse tells you to schedule a family trip in December, it would be silly to think they are referencing the tenth month of the year because of the etymology.

  1. January – named after Janus, the Roman god of beginnings and transitions, who had two faces that looked both forward and backward.
  2. February – named after the Latin term “februum,” which means purification, as this was the month in which Romans held their purification ceremonies.
  3. March – named after Mars, the Roman god of war.
  4. April – its origin is uncertain, but some believe it may be derived from the Latin word “aperire,” which means “to open,” as this is the month when buds and flowers begin to open.
  5. May – named after the Greek goddess Maia, who was associated with fertility and growth.
  6. June – named after the Roman goddess Juno, who was the patroness of marriage and the wife of Jupiter.
  7. July – named after Julius Caesar, the Roman emperor who reformed the calendar and added this month to honor himself.
  8. August – named after Augustus Caesar, the first Roman emperor and successor of Julius Caesar, who also added a month to the calendar and named it after himself.
  9. September – derived from the Latin word “septem,” which means “seven,” as it was originally the seventh month of the Roman calendar.
  10. October – derived from the Latin word “octo,” which means “eight,” as it was originally the eighth month of the Roman calendar.
  11. November – derived from the Latin word “novem,” which means “nine,” as it was originally the ninth month of the Roman calendar.
  12. December – derived from the Latin word “decem,” which means “ten,” as it was originally the tenth month of the Roman calendar.

Similarly, when God commands the believers to fast during Ramadan, this is not meant to be mysteriously deconstructed but something that is well established.

[2:185] Ramadan is the month during which the Quran was revealed, providing guidance for the people, clear teachings, and the statute book. Those of you who witness this month shall fast therein. Those who are ill or traveling may substitute the same number of other days. GOD wishes for you convenience, not hardship, that you may fulfill your obligations, and to glorify GOD for guiding you, and to express your appreciation.

 شَهْرُ رَمَضَانَ ٱلَّذِىٓ أُنزِلَ فِيهِ ٱلْقُرْءَانُ هُدًى لِّلنَّاسِ وَبَيِّنَـٰتٍ مِّنَ ٱلْهُدَىٰ وَٱلْفُرْقَانِ فَمَن شَهِدَ مِنكُمُ ٱلشَّهْرَ فَلْيَصُمْهُ وَمَن كَانَ مَرِيضًا أَوْ عَلَىٰ سَفَرٍ فَعِدَّةٌ مِّنْ أَيَّامٍ أُخَرَ يُرِيدُ ٱللَّهُ بِكُمُ ٱلْيُسْرَ وَلَا يُرِيدُ بِكُمُ ٱلْعُسْرَ وَلِتُكْمِلُوا۟ ٱلْعِدَّةَ وَلِتُكَبِّرُوا۟ ٱللَّهَ عَلَىٰ مَا هَدَىٰكُمْ وَلَعَلَّكُمْ تَشْكُرُونَ

How would one determine?

Another fundamental problem that people who claim the Islamic calendar should be based on the lunisolar calendar is that there is no consensus on how this calendar should be constructed. Some claim that a lunar month should be added to every third year, but where in the Quran do they get this understanding of 13 months? Why the third year? Where in the third year should this be placed? Even if we add a 13th month on the third year, this does not perfectly align as other adjustments will still be needed to be made to offset the difference?

If, on the other hand, days are to be added to months to make the lunar and solar cycles align, when should the days be added? Who is authorized to decide this?


Occam’s Razor, also known as the principle of parsimony, is a problem-solving principle that states that when presented with multiple explanations for a phenomenon or event, the simplest explanation is most likely to be the correct one. The basic idea behind Occam’s Razor is that, all other things being equal, simpler explanations are more likely to be true than complex ones. This is because complex explanations require more assumptions and are, therefore, more prone to error, while simpler explanations are less likely to contain errors.

Based on Occam’s Razor, a simpler explanation is that the Quran describes two systems for calculating the year, one solar and the other lunar. The religious rites are based on the lunar calendar, and Ramadan is the ninth month of the lunar calendar, which deviates about 11 days from the solar calendar each year.

The alternative is that the entire system is wrong. That there is a new Islamic calendar that needs to be created that was never known in history, and somehow we have to arbitrarily decide how exactly one is to adjust this calendar to reconcile these differences, and not to mention it causes numerous contradictions to the verses of the Quran.

From my experience of discussing with people who have many of these counter understandings is that they view anything done by traditionalists as wrong, so therefore, they look to do the opposite of whatever they see the mainstream Muslims doing. Except it is irrational to think that everything a group does is wrong, and therefore one must always do the opposite. God told us that we are to be an impartial community and not be swayed by the biases that we may have.

[2:143] We thus made you an impartial community, that you may serve as witnesses among the people, and the messenger serves as a witness among you. We changed the direction of your original Qiblah only to distinguish those among you who readily follow the messenger from those who would turn back on their heels. It was a difficult test, but not for those who are guided by GOD. GOD never puts your worship to waste. GOD is Compassionate towards the people, Most Merciful.

 وَكَذَٰلِكَ جَعَلْنَـٰكُمْ أُمَّةً وَسَطًا لِّتَكُونُوا۟ شُهَدَآءَ عَلَى ٱلنَّاسِ وَيَكُونَ ٱلرَّسُولُ عَلَيْكُمْ شَهِيدًا وَمَا جَعَلْنَا ٱلْقِبْلَةَ ٱلَّتِى كُنتَ عَلَيْهَآ إِلَّا لِنَعْلَمَ مَن يَتَّبِعُ ٱلرَّسُولَ مِمَّن يَنقَلِبُ عَلَىٰ عَقِبَيْهِ وَإِن كَانَتْ لَكَبِيرَةً إِلَّا عَلَى ٱلَّذِينَ هَدَى ٱللَّهُ وَمَا كَانَ ٱللَّهُ لِيُضِيعَ إِيمَـٰنَكُمْ إِنَّ ٱللَّهَ بِٱلنَّاسِ لَرَءُوفٌ رَّحِيمٌ

One thought on “Islamic Calendar vs. Lunisolar

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